let qs = require("querystring");
qs.parse()   //字符串转json
console.log(qs);
// {
//   unescapeBuffer: [Function: unescapeBuffer],
//   unescape: [Function: qsUnescape],
//   escape: [Function: qsEscape],
//   stringify: [Function: stringify],  对象转字符串
//   encode: [Function: stringify],
//   parse: [Function: parse],   字符串转json
//   decode: [Function: parse]
// }